Cutting metal using an automated machine cutting torch requires significant intervention from the machine operator in order to start and to adjust the cutting process. There is significant skill associated with setting up machine cutting torches, since often no two cutting torches carry the same parameters in set up. The cutting torch requires manual adjustment of oxygen and fuel gas pressure and flow rates during start-up. On each use, the flame of the cutting torch is ignited using an ignition device. Frequently, the ignition device has to be adjusted for good ignition. The oxygen and fuel gas pressure and flow rates are also often adjusted during operation.
The adjustments are conducted based upon operator experience and are made to the operator's best ability. The operator will often also change the nozzle, connected to the cutting torch, due to maintenance requirements or set up changes. This typically involves waiting for the cutting torch system to cool, unscrewing the nozzle using special wrenches, and thereafter replacing the nozzle. Following this, the cutting torch has to be set up once again. The nozzle often becomes blocked during operation due to spatter and incorrect flame set up. As a result, the cutting machine has to be stopped, the nozzle changed, and the system set up yet again. Also, during nozzle change there is no measurement or reflection of critical parameters such as gas pressure and flow rate.
Monitoring the consumption of gas is a further problem for the operator. As set up is purely manual, the gas consumption may vary significantly each time the cutting machine is used. Therefore, it is very challenging to predict the gas consumption and related costs.
The above described indicates that there is much room for improvement of current automated machine cutting torch systems.
Usually, a separate ignition device, such as an external torch or lighter, is used for igniting the cutting torch. Such an external ignition device requires that there is sufficient free space around the cutting torch, and also an additional fuel gas supply. An external solution also requires more spare parts, it makes the cutting machine more complicated, and it is necessary to adjust the ignition device to the correct position in order to ensure proper functioning. Further, external ignition devices are very frequently damaged or destroyed by the cutting process. Hence, there is more chance of function failure when using an external ignition device.
Existing internal ignition systems require additional supply of both oxygen and fuel gas, using two independent control valves, to be installed in the hazardous area. This leads to an expensive and complex solution which is difficult to control and set up. Further, an additional channel is needed inside the cutting torch for delivery of the ignition mixture to an area close to the ignition plug. One such internal ignition device is disclosed in U.S. Pat. No. 5,393,223.
Usually, cutting oxygen pressure is not measured at all at the cutting torch itself, which means that exact information about an important process parameter is missing. Pressure is normally measured at the pressure gauge on the pressure regulator or at the proportional valve inside the cutting machine, which is not sufficiently accurate. This is due to the oxygen pressure drop in the pipelines, the hoses, and other components arranged between the pressure regulator and the cutting torch.
The pressure may also be measured by using an additional gauge arranged externally between the hose and the cutting torch. However, the accuracy and life-time of such a solution is too low and its complexity is too high. Further, it is not always possible to use such an additional gauge.
The lack of exact information about the cutting oxygen pressure prevents simple optimization of the process parameters and causes a lower performance than necessary for the cutting process.
Nozzles are often changed manually by the operator, using special wrenches. This is a problem since the procedure takes time, and there is a risk of applying an excessive tightening torque, resulting in damages to the connecting thread and the sensitive nozzle surface.
A further problem is associated with adjusting the distance between nozzle and work piece such that the nozzle always is arranged at a correct height. One known solution is to connect each cutting torch to a separate sensor. However, such sensors take up valuable space within in the cutting machine, limit the movements of the cutting torch, are easily damaged by spatter, and often moves out of alignment such that the measured distance differs from the actual distance between nozzle and work piece.
As mentioned above, an automated machine cutting torch requires significant intervention from the operator in order to start up and to adjust the cutting process. Most adjustments are done based upon operator experience and are made to the operator's best ability. Hence, there are difficulties associated with achieving a correct set up and adjustment of oxygen and fuel gas parameters in response to the actual nozzle used.
As also mentioned above, a cutting torch usually requires manual cleaning and maintenance, e.g. nozzle changes. This is usually done based upon operator experience and is made to the operator's best ability. Nozzle change typically involves waiting for the cutting torch system to cool, unscrewing the nozzle using special wrenches, and thereafter replacing the nozzle.
Nozzles are usually cleaned manually using a set of specific tools in order to remove spatter and in order to clean the surfaces. Nozzle maintenance is a task often performed with little precision. Operators use basic skills to clean the nozzle, but if it is done incorrectly it can significantly reduce the performance of the nozzle, and hence the torch, and could lead to safety issues. For example, if the cutting oxygen channel is opened up incorrectly, an unbalanced flow of oxygen could arise which will lead to a sub-optimal cutting profile and could also lead to a flashback of excess oxygen into the nozzle and cutting torch.